Conventional fertilizers are granulated or compacted from mixtures of the constituent nutrients that are utilized to form the fertilizers. In some formulations, various additives, such as crop chemicals or “agrochemicals” are added to the mixtures in order to achieve additional goals in the plant products beyond fertilization. In many instances, the agrochemicals are added to the mixture of constituent nutrients and then granulated or compacted with the mixture to yield a finished product. Inorganic fertilizers such as ammonium sulfates, ammonium nitrates, potassium nitrates, potassium chlorides, potassium sulfates, and the like, all are well known. Methods of manufacturing these inorganic fertilizers, as well as methods of processing the fertilizers into particles via prill and granulation techniques, also are well known.
Particulate or granulated fertilizers, stored in bulk, will absorb moisture from the atmosphere at rates depending on the chemical composition of the fertilizer, temperature of the fertilizer, and the vapor pressure of water in the air (i.e., relative humidity in the environs where the fertilizer is stored). Also, the granular fertilizer particles often tend to cake when stored and transported in bulk such that substantial amounts of the initial free-flowing particulate fertilizer agglomerates into solid, substantially integral masses. This is colloquially referred to in the art as “caking” of the fertilizer. Softened granule can experience greater degree of abrasion and dusting. Thus, due to the incidence of caking and dusting, it is generally understood that the quality of particulate fertilizers may be improved by reducing their moisture content during production and by preventing moisture absorption during storage. This is especially true for fertilizers stored in large bulk piles where no dehumidification is provided, as is common practice in the industry.
One common method to prevent moisture absorption into the fertilizer granules is the application of oils or waxes to the fertilizer granules. Oils and waxes, being inherently hydrophobic, serve to protect the fertilizer granules from atmospheric moisture. However, due to the varied size and shape of fertilizer granules, and due to processing and storage conditions, it has been observed that the application of oils and waxes cannot fully prevent moisture absorption. As such, even with this application, water uptake, and the resultant caking and dusting, have remained a problem.
Thus, there remains a need in the art for improved fertilizer coatings and improved methods for manufacturing fertilizer coatings. Particularly, it would be desirable to provide fertilizer coatings that more fully inhibit the uptake of water, thereby reducing the incidence of dusting and caking, as compared with prior art coatings based solely on waxes or oils. Still further, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.